Many contagious diseases spread through carriers such as birds and mosquitoes. These vectors in turn move with heat and rainfall. With this in mind, researchers have begun to use satellite data to monitor the environmental conditions that lead to disease. “Ideally, we could predict conditions that would result in some of these major outbreaks of cholera, malaria, even avian flu,” says Tim Ford of the University of New England at Biddeford and co-author of a paper on the subject published this past September in Emerging Infectious Diseases.
Satellite data have already been used to map the advance of the H5N1 avian influenza in Asia. The domestic duck, a common inhabitant of Southeast Asia’s rice paddies, is one of the main carriers of the disease. Xiangming Xiao, associate director of the University of Oklahoma’s Center for Spatial Analysis, uses satellite images to map agricultural patterns in the region. These maps show where the ducks are most likely to live and thus where the avian influenza is most likely to spread.
Migratory birds also carry the virus, but their travel patterns are more difficult to predict. Xiao and his colleagues combine the satellite imagery with satellite-gathered surface-temperature data to estimate the birds’—and thereby the virus’s —trajectory. Computer models then link these environmental drivers to the spread of the flu in human populations.
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Of course, not all of the work can be outsourced to orbiting observatories. Xiao says that judging the severity of avian flu’s spread from satellite imaging required knowing details about the human populations as well—for instance, how likely certain communities were to raise ducks for poultry consumption. “Satellite monitoring has a capacity to provide consistent observation,” Xiao says. “On the other hand, the in situ observations are still very, very important, so the key is to combine those together. That is a real challenge.”
